Hearing loss linked to sleep apnoea

Experiencing sudden hearing loss may have something to do with sleep apnoea, according to a recent Taiwanese study.

The researchers found that people who had a significant, inexplicable hearing loss also suffered from sleep apnoea, statistically speaking.

While the study does not prove that sleep apnoea causes sudden hearing loss, the statistical link with the sleep disorder could point to an underlying biological mechanism, which future research may disentangle.

In sleep apnoea, people's airways stop working while they are asleep.

The condition leads to repeated falls in blood oxygen levels, and these dips in blood oxygen cause the body to wake the sleeping person.

Currently, doctors treat sleep apnoea using a machine, or by encouraging the sufferer to lose weight.

The machine works using continuous positive airway pressure (CPAP).

Seva Polotsky, a sleep apnoea researcher from Johns Hopkins University School of Medicine in the US, who did not take part in the study, said that treating apnoea might reduce hearing loss in people, but that it was not guaranteed to do so, and that researchers had more questions than answers about the nature of the link between sudden deafness and sleep apnoea.

He said that, if a patient did experience sudden hearing loss, he personally would investigate the presence of sleep apnoea as well.

Polotsky said that sleep apnoea was known to increase plaque buildup in veins and arteries, and that the condition could affect blood flow within the brain or within the ears.

Polotsky said that only future research could tell people whether sleep apnoea itself was causing deafness, or if it was due to some underlying factor.

Infections and head injuries are also often responsible for sudden hearing loss. Sudden deafness usually only happens in one ear.

People typically regain their hearing within a few weeks or a few months.

For the study, the researchers found statistics on 3,200 people who had been diagnosed with sudden deafness between 2000 and 2008.

The researchers then added statistics on over 15,000 people to the mix, all age- and gender-matched with the original 3,200 people.

Those additional people had never had hearing loss, and served as a way of averaging out gender- and age-related statistical factors, which woud interfere with the study's result.

In total, men with sudden deafness were 48% more likely to have a previous diagnosis of sleep apnoea.

The link was much less clear in women, however, and unfortunately, the researchers were not able to compensate for statistical interference caused by people's smoking and drinking.

Lead researcher Jau-Jiuan Sheu, of Taipei Medical University Hospital, and colleagues wrote that inflammation in blood vessels, sometimes leading to tinnitus, could have something to do with the hearing loss.

Polotsky said that sleep apnoea caused diabetes and high blood pressure, probably by randomly fluctuating people's oxygen levels, and that a similar mechanism could have to do with hearing loss.

He said that, however, the current study was only a signal to researchers that there could be something they had overlooked.